Investigation of suppressor polyethylene glycol dodecyl ether on electroplated Cu filling by electrochemical method

Abstract

In this paper, the use of polyethylene glycol dodecyl ether (POE) with a molecular weight of 1200 (POE-1200) as a suppressor for bottom-up electroplated copper filling of microvias was investigated. Galvanostatic measurement indicated that POE-1200 had much stronger suppression for Cu electrodeposition than PEG-8000 (polyethylene glycol with a molecular weight of 8000) and EPE-8000 (triblock copolymers of ethylene oxide–propylene oxide–ethylene oxide with a molecular weight of 8000). The strong synergistic suppression between POE-1200 and Cl⁻ led to a very thin surface thickness and excellent filling performance of microvias. The cross-sectional observations of the microvias after electroplated confirmed that changing the POE-1200 concentration from 20 to 700 ppm had little effect on the filling performance because of an unchanged positive potential difference. The adsorption strength of POE-1200 on the cathode surface was enhanced greatly only in the presence of Cl⁻, attributing to a formation of Cl⁻–Cu⁺–POE-1200 complex. The critical adsorption concentration of Cl⁻ and POE-1200 to form a saturated barrier film on the electrode surface was studied by Cu stripping peaks of cyclic voltammetry curves. In addition, the relationship between the saturated barrier of Cl⁻–Cu⁺–POE-1200 complex and the filling performance has been proposed.

Keywords:

• Suppressor
• Bottom-up filling
• Electroplated copper
• Electrochemical measurement
• Microvias